A man was arrested in San Francisco's Portola District on Tuesday morning for allegedly impersonating a law enforcement officer to avoid paying a bus fare, police said today.

At about 10:40 a.m. Tuesday, officers were doing fare inspections on a San Francisco Municipal Railway bus near Silver and San Bruno avenues when they encountered someone who could not produce a fare receipt, according to police.

When asked for identification, the man showed the officers a Department of Corrections sergeant's badge, but had no other law enforcement identification as required by law, police said.

The man, whose name has not been released, was detained and later admitted to buying the badge from someone on the street and said he had been using it to avoid paying bus fares, police said.